Carbon nanotubes were discovered by S. Ijima (Nature, vol. 354, pp. 56-58, 1991) and synthesized by T. W. Ebbesen and P. M. Ajayan (Nature, vol. 358, pp. 220-222, 1992). Theoretical studies showed that carbon nanotubes exhibit either metallic or semiconductive behavior depending on the radii and helicity of the tubules. Carbon nanotubes have interesting and potentially useful electrical and mechanical properties, and offer potential for use in electronic devices. Carbon nanotubes also feature high aspect ratios (>1000) and atomically sharp tips, which make them ideal candidates for electron field emitters, white light sources, lithium secondary batteries, hydrogen storage cells, transistors and cathode ray tubes (CRTs).
Carbon nanotubes are currently being produced by a variety of different techniques such as arc discharge (See S. Iijima et al, Nature, Helical Microtubules of Graphitic Carbon, vol. 354, pp. 56-58, 7 Nov. 1991), laser ablation (See T. W. Ebbesen and P. M. Ajayan, Large-scale Synthesis of Carbon Nanotubes, Nature, vol. 358, pp. 220-222, 16 Jul. 1992) and chemical vapor deposition (CVD) (See W. Z. Li et al., Large-scale Synthesis of Aligned Carbon Nanotubes, Science, vol. 274, pp. 1701-1703, Dec. 6, 1996). All of the above-mentioned disclosures are incorporated herein by reference.
Isotope labeling is a powerful tool in the study of nano-material growth mechanisms and in nano-sized isotope junction synthesis. Methods of isotope labeling use reactants containing different isotopes of a special element (usually light elements such as carbon, boron, nitrogen and oxygen), which are fed in designated concentrations (pure or mixed) and sequences into a nano-material synthesis process to provide in situ isotope labeling of nano-materials.
However, none of the three above-described techniques for producing carbon nanotubes, namely arc discharge, laser ablation and CVD, provides isotope-doped carbon nanotubes or a method for making isotope-doped carbon nanotubes. Therefore, what is needed is carbon nanotubes and methods for making the same.